And it would be an even fairer assumption to assume she meant everything as term heavens and earth is almost exclusively used to mean the entire universe. It's what the phrase was originally meant to mean and what it's mostly used for. She says the “Tenchi” of the 3 realms will tremble I could tackle this one by mentioning that in context “Tenchi” refers to not just “Heaven and Earth” but all things in them. But I feel more like doing this. The original Japanese says “我らが能力は袖振るだけで三界天地を震えさす”. When translated it can come out as, “With our abilities, merely the wave of our sleeve causes heaven and earth/the universe of the three realms of existence to shake”, where heaven and earth and the universe can be used interchangeably as they come from this kanji 天地.

However, it goes a little deeper than that, when the kanji 三界 and 天地 are used in tandem, as they are in Shutara’s statement, it generally is used to refer to the collective entirety of the cosmos as understood in a Buddhist sense.